The present invention relates to an aircraft deicing system, and more particularly to a dual primary deicing system for a rotor system of a rotary-wing aircraft.
Rotary-wing aircraft may encounter atmospheric conditions that cause the formation of ice on rotor blades and other surfaces of the aircraft. Accumulated ice, if not removed, can add weight to the aircraft and may alter the airfoil configuration causing undesirable flying characteristics.
One approach to ice management that has been used is thermal deicing. In thermal deicing, the leading edge portions of the rotor blades are heated to loosen accumulated ice. The loosened ice is then removed from the structural members by centrifugal forces and the airstream passing over the leading edge.
In one form of thermal deicing, heating is accomplished by electrothermal heating elements over or within the leading edges of the airfoils. Electrical energy for the electrothermal heating elements is derived from a generating source driven by one or more of the aircraft engines or transmissions. The electrical energy is intermittently supplied to provide heat sufficient to loosen accumulating ice.
Rotary wing aircraft rotor blades are particularly susceptible to icing and provide numerous challenges for electrothermal deicing systems. One difficulty relates to the refreezing of ice, which is melted with a leading edge electrothermal element as the rotor system is constantly in motion.
FAA Regulations, including 14 CFR 29.1309, and SAE ARP4761 delineate increased flight safety and redundancy requirements for rotary-wing aircraft flying under icing conditions. Various functionally acceptable rotary wing deicing systems are currently in use, however, none provide the capabilities and redundancy necessary to meet the expanded FAA regulations. Deicing systems that meet these regulations provides a competitive position over currently available rotary-wing ice protection systems.
Accordingly, it is desirable to provide an effective, reliable, and redundant rotary wing deicing system which meets FAA Regulations.